1. Field of the Invention
The present invention relates to an image processing apparatus. More specifically, the present invention relates to an apparatus, a method, and a program capable of handling an image which contains a copy-forgery-inhibited pattern image.
2. Description of the Related Art
A copy-forgery-inhibited pattern image (Japanese Patent Laid-Open No. 2001-197297) is known.
A copy-forgery-inhibited pattern image is an image to realize an effect that, where an original document having a copy-forgery-inhibited pattern image thereon is printed (e.g., after scanning to make a copy), predetermined characters or the like which are not recognized before the printing are visualized upon printing, to suppress the use of printing of a copy.
In order to realize the effect, a copy-forgery-inhibited pattern image to be generated includes two fundamental regions, that is, a region (major dot portion) at which an image identical to that on an original document remains upon printing a copy, and a region (minor dot portion) at which the image existing on the original document disappears upon the printing or thins in comparison with the image in the remaining region. In the copy-forgery-inhibited pattern image having these two regions, the two regions are substantially similar in density when the copy-forgery-inhibited pattern image is printed and output. Specifically, the thus printed and output copy-forgery-inhibited pattern image is processed in such a manner that it is difficult for humans to visually recognize macroscopic characters and others hidden upon printing an original.
An image region which is hidden upon printing an original document containing the copy-forgery-inhibited pattern image, but which appears so as to be recognized visually by humans upon printing a copy of the original document, is called a “major dot portion” or a “visualized portion.”
Further, an image region which disappears upon printing a copy, or thins in density in comparison with a latent image visualized upon the printing of a copy, is called for descriptive purposes a “minor dot portion” or a “disappeared portion.”
FIG. 1 is a view showing a state of dots at two image regions, that is, a major dot portion and a minor dot portion. As shown in FIG. 1, a copy-forgery-inhibited pattern image has a minor dot portion 101 at which dots are arranged dispersedly at a predetermined region and a major dot portion 102 at which dots are arranged in a concentrated manner. Dots which exist in the two regions, that is, the major dot portion 102 and the minor dot portion 101, can be generated by halftone dot processing or dithering that is different for the two regions.
For example, where the halftone dot processing is adopted to generate a copy-forgery-inhibited pattern image, the major dot portion 102 may be subjected to halftone dot processing at a lower number of lines per inch. Further, the minor dot portion 101 may be subjected to halftone dot processing at a higher number of lines per inch. Where dithering is adopted to generate a copy-forgery-inhibited pattern image, the major dot portion 102 may be subjected to dithering which uses a dot concentrated dither matrix. Further, the minor dot portion 101 may be subjected to dithering which uses a dot dispersion-print dither matrix.
Hereinafter, a fact that the minor dot portion disappears on printing and only the major dot portion appears (i.e., remains) is called visualization.
FIGS. 2 (a) and (b) are views showing the visualization. FIG. 2(b) is visualized upon printing a copy of the pattern shown in FIG. 2(a). FIGS. 2(a) and (b) show that where dots are arranged in a concentrated manner, they are visualized upon printing a copy, and where dots are arranged dispersedly, they are not reproduced upon printing a copy.
It is noted that copy-forgery-inhibited pattern printing shall not be limited to the above described constitution. Any constitution may be applicable as long as character strings or others can be reproduced so as to be recognized upon printing a copy. Specifically, as shown in FIG. 14, even if character strings or others are specified as a minor dot portion and shown in a state of outlined characters upon printing, the copy-forgery-inhibited pattern printing attains its aim.
Further, as shown in FIG. 17, hereinafter, a part of a copy-forgery-inhibited pattern containing characters is called a “character portion” of the copy-forgery-inhibited pattern (1701) and a part other than the part of the copy-forgery-inhibited pattern containing characters is called a “non-character portion” of the copy-forgery-inhibited pattern (1702).
In considering a copy-forgery-inhibited pattern, it is important to recognize that a dense part printed on one side of a sheet has showthrough on the other side (reverse side).
For example, in FIG. 18, a character portion 1805 is a minor dot portion on the front side 1801 of a document, while character portions 1806 and 1807 are minor dot portions on the rear side 1802 of the document. In such a case, the character portion 1805 on the front side 1801 of the document is rendered to a state of 1808 on printing and has disappeared. However, a non-character portion on the rear side 1802 of the document remains dense upon printing, and thereby this remaining dense part has showthrough. As a result, the minor dot portion 1808 which should be white is not white. As a result, the character portion 1808 on the front side of the printing is less likely to be distinguished from the periphery thereof. This is also true for the rear side. It is noted that since FIG. 16 shows the same thing as that shown in FIG. 18, the description thereof will be omitted here.
On the other hand, in FIG. 19, a character portion 1905 is a major dot portion on the front side 1901 of a document while character portions 1906 and 1907 are major dot portions on the rear side 1902 of the document. In such a case, the character portion 1905 on the front side 1901 of the document is rendered to a state of 1908 on printing and has been visualized. Further, the character portions 1906 and 1907 on the rear side 1902 of the document remain dense upon printing, and thereby the part which remains dense has showthrough. However, on the front side of the printed copy, the character portion 1908 is reliably distinguished from the periphery, although this showthrough influences the character portion. This is also true for the rear side. It is noted that since FIG. 15 shows the same thing as that shown in FIG. 19, the description thereof will be omitted here.
An object of the present invention is to provide an apparatus capable of preventing a failure in distinguishing a character portion in a copy-forgery-inhibited pattern image from the periphery thereof due to showthrough after printing a copy.